Are sports betting bonuses +EV?

I'm thinking of clearing a Boogster bonus for the equivilence of 40 dollars for BetRoyal.

For a deposit of 100 dollars I get a 10 dollar bonus.

It only takes 100 dollars wagered to clear.

I've never done sports betting (but i know how it works). I figure i'll make ten $10 bets on the team with the advantage.

The vigorish is like 20% i think so unless I'm mistaken my EV is -10 but its + 30 w/ boogster.

Is this worth the risk? Or should I just stick to clearing poker sites.

(I'd hate for this to turn into another casino bonus travesty).

{moved from On-Line Poker Rooms}